1. Field of the Invention
The present invention relates to a method of monitoring the performance of a working tool and more particularly to a method of monitoring of the performance of a working tool by sensing differential torque or force associated with the working tool at various points in a work cycle and utilizing the sensed information to determine whether the working tool meets predetermined standards.
Methods of monitoring the performance of working tools are well known in the art. The known methods include sensing torque associated with the working tool and setting a high stop limit when the torque reaches a predetermined magnitude. Another known method includes sensing current or power. However when the current or power of a system is sensed the information is filtered or smoothed by the mass of the system and many significant pieces of information are lost by this smoothing or filtering process.
The known systems do not provide for sensing differential torque during a increment of a work cycle between a working tool and a workpiece. The determination of differential torque can be utilized to determine whether the working tool is functioning properly relative to the workpiece. The differential torque measurement can be utilized to shut down a machine tool if the working tool is not functioning properly such as if the tool is broken or dull and/or can be utilized to activate a warning signal indicating that the cutting tool is getting dull and its replacement time is approaching.
2. Prior Art
The Gilmore et al patent application Ser. No. 398,021 filed July 14, 1982 now U.S. Pat. No. 4,489,617, discloses a quality control method wherein differential torque is utilized to test a mechanical assembly which moves through a cycle. Smith et al does not disclose utilizing differential torque to monitor the condition of a cutting tool.
The Abbatiello U.S. Pat. No. 3,836,834 discloses a machine protection system wherein the system initiates shut down whenever an average force suddenly changes its level by a preselected factor (dynamic error). Abbatiello does not sense torque or force differential but rather produces a dynamic force comparator which is responsive to the average signal output and the instantaneous signal output and which produces a shut down when the instantaneous signal level exceeds a preselected multiple of the average signal level.
The Forath U.S. Pat. No. 3,545,310 runs a high low check but only at a no load level. Forath mainly looks at the torque gradiant to determine tool wear and does not look at dynamic force differential during cutting. Watanabe U.S. Pat. No. 3,834,615 also disclosed a method of monitoring a machine tool wherein the torque gradiant is utilized to sense tool wear.
Frecka U.S. Pat. No. 4,237,408 is an example of a system which assumes that power and torque is indirectly related. Frecka measures power to determine tool wear. Kobayashi U.S. Pat. No. 4,260,986 also assumes that power and torque are directly related and compares high-low power signals with a reference to determine when a bad tool is sensed.